User Guide

Introducing the BIOS
User’s Manual
4-19
ACPI or not, please contact the device or add-on card manufacture for more information. If you want to
know more about ACPI specifications, please go to the address below for more detailed information:
http://www.teleport.com/~acpi/acpihtml/home.htm
ACPI requires an ACPI-aware operating system. ACPI features include:
! Plug and Play (including bus and device enumeration) and APM functionality normally contained in
the BIOS.
! Power management control of individual devices, add-in cards (some add-in cards may require an
ACPI-aware driver), video displays, and hard disk drives.
! A Soft-off feature that enables the operating system to power off the computer.
! Support for multiple wake-up events (see Table 4-5-1).
! Support for a front panel power and sleep mode switch. Table 4-5-2 describes the system states based
on how long the power switch is pressed, depending on how ACPI is configured with an ACPI-aware
operating system.
System States and Power States
Under ACPI, the operating system directs all system and device power state transitions. The operating
system puts devices in and out of low-power states based on user preferences and knowledge of how
devices are being used by applications. Devices that are not being used can be turned off. The operating
system uses information from applications and user settings to put the system as a whole into a low-power
state.
The table below describes which devices or specific events can wake the computer from specific states.
Table 4-5-1: Wake Up Device and Events
These device/events can wake up the
computer……
……from this state
Power switch Sleeping mode or power off mode
RTC alarm Sleeping mode or power off mode
LAN Sleeping mode or power off mode
Modem Sleeping mode or power off mode
USB Sleeping mode
PS/2 keyboard Sleeping mode
PS/2 mouse Sleeping mode
Table 4-5-2: Effect of Pressing the Power Switch
If the system is in this
state……
……and the power switch is
pressed for
……the system enters this
state
Off Less than four seconds Power on
On More than four seconds Forced power off
On Less than four seconds Defined by OS
Sleep Less than four seconds Wake up
ACPI Standby State:
Three options are available: S1 ( S3 ( Auto. The default setting is S1. In this case, BIOS will
automatically judge your system can running on which state. Generally, ACPI has six states: System S0
state, S1 state, S2 state, S3 state, S4 state, S5 state. S1 and S3 states are described below: